1. Field of the Invention
The present general inventive concept relates to a light scanning unit, and more particularly, to a beam detector generating a synchronous signal by detecting a light beam and a light scanning unit having the same.
2. Description of the Related Art
Light scanning units such as laser scanning units (LASS) are used for image forming apparatuses such as copiers and laser printers. A light scanning unit scans light emitted from a light source onto a photosensitive medium of an image forming apparatus to form an electrostatic latent image on an outer circumference surface of the photosensitive medium. A beam detector for generating a synchronous signal by receiving a light beam emitted from the light source is provided in the light scanning unit.
FIG. 1 is a cross-sectional view of a conventional beam detector 10. Referring to FIG. 1, the beam detector 10 includes a beam detection sensor 12 having a light receiving portion 13 for receiving a light beam, a slit member 20 having a slit 21 for controlling a time when a synchronous signal of the beam detection sensor 12 is generated by partially blocking the light beam incident on the light receiving portion 13, and a beam convergence lens 15 for focusing the light beam passing through the slit 21. The slit member 20 of the beam detector 10 is displaced in a horizontal direction as indicated by an arrow, earlier or later than the time when the synchronous signal of the beam detection sensor 12 is generated. However, since an amount of horizontal displacement of the slit member 20 cannot be accurately controlled, it is difficult to accurately control the time of generating the synchronous signal.